Metal Lathe Tutorial 3 Facing

hello Internet my name is Quinn this is blondie hacks this is late skills number three facing this is a series of quick videos on how to get started in machining if you like this content I post exclusive project videos on patreon so go ahead and subscribe there is a link down in the description ok let's dive in so facing is machining the end of the work on the lathe and it's generally the first operation you're going to do on any part the main purpose of it is that it not just makes it look nice but it's giving you your first reference surface what that means is that you know you might typically you're gonna have like a bandsaw cut or maybe a pinch cut from a shear from the factory on fresh stock and the point is that even though it might look Square and flat you'd actually don't know anything about this surface you know it might be off by one degree there might be a low spot in the middle that you can't see any UNMISS is has to be suspect you don't know anything about it after it's machined we know a lot about it now we know it's parallel to this Chuck face it's perpendicular to these ways and by extension if we turn the ice outside diameter this we know this angle right here will be exactly ninety degrees and once it's machined then now we can start you know doing layout off of that we can take measurements that will be accurate from that surface so facing gives us our first reference surface on the stock and before you do any operation on the lathe it's very important that your tool height be correct the tool always has to be on center and an easy way to set that up for rookies is to just turn your tool post around and line it up with a center set in your tail stock and just get down real low and eyeball but the top surface of that tool is right on the very center of the end of that the top surface of this is what's doing the cutting and this guy this point right here in the live Center you know is on the center axis of the lathe so if you get those two guys lined up your tool height is correct the next thing to think about is the RPM of your spindle every material is going to have an ideal surface rate that that it wants and so you need you can do some math on the diameter of the part to calculate all that and so on but with facing because we're going from the outside in towards the center the effective surface speed decreasing so generally end up just kind of setting a compromise or for a large-diameter part if you have a lathe with a variable speed control on the spindle such as this one you can actually increase the speed as the tool bit gets towards the center but for for most most of time you just set a decent compromise I'm going to set it at 500 rpm for this 360 free machining breaths next to make sure that the angle on your tool post is correct you want good clearance angles on on the tool bit that you're using and you also need to make sure that the cross slide is going to reach all the way to the center you know on a lot of smaller smaller leaves and hobbyist lathes especially at limited travel on the cross slide so make sure that your tool is actually going to reach all the way into the center there before bottoming out on the stops the next step is to touch off remember we don't know anything about this surface and we don't know where the high spot is so you want to control your depth of cut at all times so you know a good start for a facing cut might be 20,000 s but we don't know where 20,000 s is yet so an easy way to do that is just put your tool bit towards the outside edge because if it's like a bandsaw cut the high point is going to be on the outside edge and then run the lathe and then bring your tool in nice and slow until you hear it start touching off on any part of the work let's do that now okay right there I got a chip on that spot if I bring my cross light out a little bit you can see I'm just getting some chips coming out of there so we're gonna call this touched off and now we can bring our tool bit out clear of the work and then down here on my hand wheel I can advance ten twenty thousandths and then lock that carriage you always lock the carriage when you're facing otherwise the cutting forces will push that carriage back out again so now I know that I'm cutting no deeper than twenty thousands anywhere on the part so now I can just start winding this in and this is always going to be an interrupted cut at first because again that surface is not machined so it's not flat so generally you're going to do a couple of passes and you keep doing passes until you don't see any more of those saw marks so after that first pass shut everything down but don't move any of the controls because that tool bit is now forming a reference surface and you'll want to lose that position but I'm gonna just turn the stock here by hand to show you what we've got so you can see how this is all nice and machine we've got a mirror finish on there but this over here you can still see the bandsaw cut marks so this is how you know we're not quite done yet so now I can wind this out going another twenty thousand and again I know I'm cutting no deeper than twenty thousand anywhere and I just keep doing that until everything is mirror finish all the way down and this is the result we're looking for we got a mirror finish all the way across that part is now faced but hold on what if you end up with something like this I did everything correctly or so I think and I ended up with a little nubbin right here what that means is that my tool height wasn't quite correct if I bring this in you can see that my tool actually goes underneath that nubbin so my tool is just a little bit too low and in fact facing operations are a really good way to actually just check and set your tool height if there's no nub and left over then you know your tool height is correct if the tool height is a little too high you won't get a nubbin but as you get towards the center it'll push harder and harder you'll feel resistance on the cross slide because what's happening is while the tool is cutting up here the bottom part of the tool is starting to rub down here because there isn't enough clearance underneath so remember that top surface is doing the cutting so that top surface has to be exactly on the center line to avoid any rubbing and to avoid any nubbins so that's facing in a nutshell it's the first and most fundamental operation you're ever gonna do on a lathe so I hope you found this useful please do subscribe on patreon and we will see you next time thanks for watching you